The easiest way may be to hand them a business card with your SFI link on it. If the opportunity is there to introduce SFI is present, and they see that you are excited about it, they will want to look too.
You can be honest and tell them that you are not good at talking about SFI, but that there are many people that, after they sign up for free, will answer all questions.
The important thing is that you don't sound like a salesman. You are a friend, offering help.
